Punching apparatus for stamping and method for producing the same

ABSTRACT

A stamping punch of a punching apparatus including a grip member provided with crosspieces formed between long grooves on side walls of a rectangular parallelepiped, and a plurality of punch members which are formed integrally with the grip member. The respective punch members are arranged in parallel to one another. A plurality of holes are defined on a punch holder. A large amount of adhesive is contained in the gap between joining surfaces when the grip members of the stamping punches are inserted and secured into the respective holes. Accordingly, the positional accuracy of the punch member is improved, the accuracy of the hole defined through a workpiece is improved, and it is possible to eliminate any fear of occurrence of defect in shape. Further, the rigidity of the punch member can be improved, the stripper is prevented from application of unbalanced load, and the punch is easily exchangeable.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a division of U.S. application Ser. No.09/401,227, filed Sep. 22, 1999, now allowed, the entirety of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a punching apparatus forstamping and a method for producing the same for applying perforatingmachining to a sheet-shaped workpiece.

[0004] 2. Description of the Related Art

[0005] A punching apparatus for stamping has been hitherto used fordefining a plurality of holes through a sheet-shaped workpiece by meansof stamping machining. Such a punching apparatus for stamping isconstructed as follows. That is, a plurality of lengthy holes 1003 aredefined through a metal plate or the like by means of electric dischargemachining (see FIG. 14A). The holes are precisely finished by means ofwire electric discharge machining to produce a punch holder 1002 (seeFIG. 14B).

[0006] As shown in FIG. 15, lengthy punch members 1004 having asubstantially rectangular cross section are inserted into the holes 1003which are defined through the punch holder 1002 as described above.Roots of the punch members 1004 are secured to the punch holder 1002 byusing, for example, an adhesive.

[0007] The punch members 1004 are slidably inserted into lengthy holes1006 of a stripper 1005 which is provided for the punching apparatus forstamping. Further, the punch members 1004 are inserted into lengthyholes 1008 which are defined through a die 1007.

[0008] When a plurality of lengthy holes 1011 are bored through aworkpiece 1009 such as a green sheet by using the stamping punchingapparatus 1001 constructed as described above, the workpiece 1009 isplaced on the die 1007. When the punch members 1004 and the stripper1005 are moved downwardly, the lower surface of the stripper 1005firstly abuts against the upper surface of the workpiece 1009.Subsequently, the punch members 1004 are moved downwardly to apply theperforating machining to the workpiece 1009.

[0009] However, in the case of the conventional stamping punchingapparatus 1001 as described above, it is necessary that the hole 1003 isformed to be slightly larger than the dimension of the punch member 1004in order to insert the punch member 1004 into the hole 1003. For thisreason, a slight gap A is generated between the punch member 1004 andthe wall for forming the hole 1003 of the punch holder 1002. Therefore,it is difficult to improve the positional accuracy of the respectivepunch members 1004.

[0010] On the other hand, the holes 1006 defined through the stripper1005 are also formed to be slightly larger than the rectangulardimension of the punch member 1004. For this reason, a gap B existsbetween the punch member 1004 and the wall of the hole 1006. As aresult, the error in positional accuracy of the punch member 1004 isallowable within a range of the gap B. Therefore, a problem arises inthat the positional accuracy and the shape accuracy are lowered for thehole 1011 of the workpiece 1009 subjected to the perforating machiningperformed by the stamping punching apparatus 1001. Further, anyunbalanced load is exerted on the stripper 1005 through which the punchmember 1004 is inserted. It is feared that the punch member 1004 and thestripper 1005 may be broken.

[0011] The hole 1008 of the die 1007 is formed to be larger than therectangular dimension of the punch member 1004 so that the punch member1004 is reliably inserted therethrough even when any error exists in therectangular dimension of the punch member 1004 or in the position of thepunch member 1004 with respect to the punch holder 1002. When the pitchbetween the punch members 1004 is small, the gap between the hole 1008and the adjoining hole 1008 is narrow. Therefore, the following problemarises. That is, if there is any difference in size between the gaps C1and C2 generated between the punch member 1004 and the walls for formingthe hole 1008 of the die 1007, any inclination (deformation in the rightor left direction in FIG. 15) is caused by the gap A in the non-punchedportion D of the workpiece 1009, resulting in defect in shape.

[0012] Although the respective punch members 1004 are formed to belengthy in the vertical direction in FIG. 15, their first ends aremerely supported by the punch holder 1002. Therefore, it is feared thatthe punch member 1004 may be deformed by the load exerted on the punchmember 1004 during the stamping, or the punch member 1004 is broken dueto the buckling.

[0013] When the punch member 1004 is exchanged due to any breakage orthe like, it is necessary to perform the operation to scrape the curedadhesive by using a grinder or the like. However, during this operation,when the pitch for the punch members 1004 is small, for example, whenthe punch members 1004 are arranged at a pitch of not more than 0.6 mm,then the following inconvenience appears. That is, for example, a highlysophisticated technique is required for the operation to detach andattach only the punch member 1004 which is required to be exchanged.Further, it is complicated to perform the operation to insert all of thepunch members 1004 into the holes 1006 of the stripper 1005 again.

SUMMARY OF THE INVENTION

[0014] The present invention has been made in order to dissolve thevarious problems described above, an object of which is to provide apunching apparatus for stamping and a method for producing the same inwhich the positional accuracy and the shape accuracy of the hole definedthrough a workpiece are improved by improving the positional accuracy ofa punch member, the rigidity of the punch member can be improved, astripper is prevented from application of any unbalanced load, and thepunch member can be easily exchanged.

[0015] According to the present invention, there is provided a punchingapparatus for stamping for applying perforating machining to a workpieceby using punch members, the apparatus comprising a punch holder securedto an upper die; a die member secured to a lower die; a plurality ofgrip members detachably fastened to the punch holder; and the pluralityof punch members formed on each of the plurality of grip members.

[0016] Accordingly, it is unnecessary to individually assemble the punchmembers to the punch holder one by one, and hence there is no assemblingerror. Therefore, the positional accuracy of the punch member isimproved, and the positional accuracy and the shape accuracy can beimproved for the hole to be defined through the workpiece. Further, forexample, even when the punch member has a slender pin-shapedconfiguration, it is possible to reduce the occurrence of fracture andbreakage, because its rigidity is enhanced, which is preferred.

[0017] It is preferable for the punching apparatus for stampingaccording to the present invention that the grip member and the punchmembers are formed in an integrated manner by using a single material.

[0018] Accordingly, it is unnecessary to separately produce the gripmember and the punch members so that they are assembled to one another.Therefore, the production steps are simplified, and any defect does notoccur in positional accuracy of the punch member upon assembling. It ispossible to further enhance the rigidity of the punch member.

[0019] It is preferable for the punching apparatus for stampingaccording to the present invention that the grip member has arectangular cross section, and a plurality of grooves are formed on atleast two opposing side walls of the rectangular cross section; and thepunch holder is defined with a hole having a rectangular cross sectioncorresponding to the grip member, and the grip member is fitted to thepunch holder with a gap such that crosspieces formed between the grooveson the side walls of the grip member slidably contact with side walls ofthe hole of the punch holder. In this arrangement, it is more preferablethat the crosspiece on the side wall of the grip member is formed tohave a circular arc-shaped configuration. It is also preferable that thecrosspiece involves a circular arc-shaped configuration with its topformed to be flat.

[0020] Accordingly, when the grip member integrally provided with thepunch members is fitted to the hole of the punch holder, a large amountof adhesive can be contained in the gap between joining surfaces. Theexpanding effect of the adhesive is also exerted after the joining,because the joining surfaces of the grip member have a large areal size.Thus, it is possible to enhance the adhesive force between the gripmember and the punch holder. The adhering performance is excellent ascompared with the case in which a flat surface of a grip member ismutually joined to a flat surface of a punch holder.

[0021] In the punching apparatus for stamping according to the presentinvention for applying the perforating processing to the workpiece byusing the punch members, it is preferable that the grip member is formedby being divided into two or more holding members, a plurality ofgrooves having a triangular cross section are formed on a joiningsurface of one holding member of the two holding members to be joined ata dividing surface, and a joining surface of the other holding member isformed to be flat; each of the punch members is formed to have apin-shaped configuration; and first ends of the plurality of punchmembers are inserted into holes defined at the dividing surface.

[0022] Accordingly, the grip members and the punch members can be easilyformed at a high degree of accuracy in an individual manner.

[0023] According to another aspect of the present invention, there isprovided a method for producing a punching apparatus for stamping, themethod being preferably used and comprising the steps of using aprism-shaped block as a material for the grip member and the punchmembers; machining a plurality of parallel long grooves separated fromeach other by arbitrary spacing distances on two opposing side walls ofthe prism-shaped block; machining tops of crosspieces formed between thelong grooves to have a circular arc-shaped configuration; machining longgrooves having an arbitrary depth on another side wall so that the longgrooves communicate with the long grooves on the two side walls;simultaneously forming thereby the grip member including the pluralityof long grooves and the circular arc-shaped crosspieces formed betweenthe long grooves provided on the two opposing side walls and theplurality of punch members each having a lengthy rectangular crosssection with its both ends provided with circular arc-shaped portions;and defining a plurality of holes each having a rectangular crosssection on the punch holder on the other hand; wherein the grip memberis fitted to the punch holder with a gap such that the crosspiecesformed on the side walls of the grip member slidably contact with sidewalls of the hole of the punch holder.

[0024] In this arrangement, it is also preferable that the circulararc-shaped top of the crosspiece formed on the side wall of the gripmember and the circular arc-shaped portion at both ends of the punchmember are deformed to include flat portions. It is also allowable toomit the step of machining and forming the plurality of parallel longgrooves on the side walls of the prism-shaped block by machining andforming the plurality of parallel circular arc-shaped crosspieces on theside walls of the prism-shaped block (see FIG. 7B).

[0025] Accordingly, it is possible to further simplify the operationsteps for integrally producing the grip members and the punch members,which is preferred.

[0026] The above and other objects, features, and advantages of thepresent invention will become more apparent from the followingdescription when taken in conjunction with the accompanying drawings inwhich a preferred embodiment of the present invention is shown by way ofillustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 shows a longitudinal sectional view illustrating a punchingapparatus for stamping according to a first embodiment of the presentinvention;

[0028]FIG. 2 shows an exploded perspective view illustrating a lower dieof the punching apparatus for stamping shown in FIG. 1;

[0029]FIG. 3 shows an exploded perspective view illustrating an upperdie of the punching apparatus for stamping shown in FIG. 1;

[0030]FIG. 4 shows a perspective view illustrating a stamping punch usedfor the punching apparatus for stamping shown in FIG. 1;

[0031]FIG. 5 shows a perspective view illustrating a first modifiedembodiment of the stamping punch;

[0032]FIG. 6 shows a perspective view illustrating a second modifiedembodiment of the stamping punch;

[0033]FIG. 7A shows a step of machining a material to form a rectangularparallelepiped shaped object;

[0034]FIG. 7B shows a step of machining the rectangular parallelepipedshaped object to form long grooves on its side walls;

[0035]FIG. 7C shows a step of machining projections between the longgrooves to form circular arc-shaped crosspieces;

[0036]FIG. 7D shows a step of finally forming a grip member and punchmembers in an integrated manner;

[0037]FIG. 8 shows a plan view as viewed from a side of the stampingpunch in order to explain a fitting state of the stamping punch and thepunch holder according to the first embodiment of the present invention;

[0038]FIG. 9 shows a plan view as viewed from a side of the stampingpunch in order to explain a fitting state of the stamping punch and thepunch holder according to a modified embodiment of the first embodimentof the present invention;

[0039]FIG. 10 shows a partial magnified sectional view illustrating astate in which a stripper abuts against a sheet material, depicting themethod for using the punching apparatus for stamping shown in FIG. 1;

[0040]FIG. 11 shows a partial magnified sectional view illustrating astate in which the sheet material is subjected to perforating machining,depicting the method for using the punching apparatus for stamping shownin FIG. 1;

[0041]FIG. 12 shows a perspective view illustrating a stamping punch anda fixing jig for punch members used for a punching apparatus forstamping according to a second embodiment of the present invention;

[0042]FIG. 13 shows a partial magnified plan view illustrating thestamping punch and the fixing jig shown in FIG. 12;

[0043]FIG. 14A shows a partial magnified schematic longitudinalsectional view illustrating a state in which holes are formed through apunch holder;

[0044]FIG. 14B shows a partial magnified schematic sectional viewillustrating a state in which the holes are finished by means of wireelectric discharge machining; and

[0045]FIG. 15 shows a partial magnified schematic longitudinal sectionalview illustrating a stamping punch concerning the conventionaltechnique.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0046] The punching apparatus for stamping according to the presentinvention will be exemplified by preferred embodiments in relation tothe production method thereof, and it will be explained in detail belowwith reference to the accompanying drawings.

[0047] With reference to FIG. 1, reference numeral 10 indicates apunching apparatus for stamping according to the first embodiment of thepresent invention. As shown in FIGS. 1 and 2, the stamping punchingapparatus 10 includes a lower die attachment member 12. Holes 14 a to 14d are defined through the lower die attachment member 12. Holes 16 aredefined at the inside of the holes 14 a to 14 d. A plate-shaped lowerdie 18 is secured to an upper portion of the lower die attachment member12. Holes 20 a to 20 d, which have the same diameter as that of theholes 14 a to 14 d and which coaxially communicate with the holes 14 ato 14 d, are defined through the lower die 18. Holes 24 having steps 22are defined at the inside of the holes 20 a to 20 d so that theycommunicate with the holes 16. Main posts 26 a to 26 d, which extendupwardly, are provided in an upstanding manner in the vicinity of thecorners of the lower die 18.

[0048] A plate-shaped die-fixing plate 28 is secured to an upper portionof the lower die 18. Holes 30 a to 30 d, which have the same diameter asthat of the holes 20 a to 20 d and which coaxially communicate with theholes 20 a to 20 d, are defined in the vicinity of the corners of thedie-fixing plate 28. A recess 32 is defined at an upper portion of thedie-fixing plate 28. Holes 34, which communicate with the holes 24, aredefined through the bottom for forming the recess 32. A plurality of diemembers 36, which are formed to have a rectangular parallelepiped-shapedconfiguration, are fitted to the recess 32 (see FIG. 2). The die member36 is secured to the die-fixing plate 28 by using screws 38. A pluralityof lengthy holes 40, which correspond to lengthy holes to be definedthrough a sheet material as a workpiece as described later on, aredefined through each of the die members 36.

[0049] As shown in FIGS. 1 and 3, the stamping punching apparatus 10 isprovided with an upper die attachment member 42 which is capable ofmaking approach and separation with respect to the lower die attachmentmember 12. The upper die attachment member 42 is defined with aplurality of recesses 44 and a plurality of holes 46 formed at theinside of the recesses 44. An upper die 48 is secured to a lower portionof the upper die attachment member 42. Holes 50, which have the samediameter as that of the recesses 44 and which coaxially communicate withthe recesses 44, are defined through the upper die 48. A plurality ofholes 54 having steps 52 are defined to make communication with theholes 46. Main post guides 58 a to 58 d, which protrude downwardly, areformed in the vicinity of corners of the upper die 48. The main posts 26a to 26 d are inserted into holes 60 a to 60 d of the main post guides58 a to 58 d.

[0050] A punch holder-fixing plate 62 is secured to a lower portion ofthe upper die 48. The punch holder-fixing plate 62 is defined with holes64 which communicate with the holes 50 and which have a diameter smallerthan that of the holes 50. Columnar members 66 are slidably insertedinto the hole 64. Flanges 68, which protrude outwardly, are secured byscrews 70 to upper portions of the columnar members 66. The flanges 68are displaceable in the axial direction at the inside of the holes 50.The flanges 68 abut against the upper surface of the punch holder-fixingplate 62, and thus the columnar members 66 are prevented fromdisengagement. First ends of spring members 72 abut against upperportions of the flanges 68. Second ends of the spring members 72 abutagainst ceilings for forming the recesses 44. Therefore, the columnarmembers 66 are urged downwardly by the spring members 72.

[0051] As shown in FIGS. 1 and 3, a rectangular recess 82 is defined ata lower portion of the punch holder-fixing plate 62. Holes 84, whichcommunicate with the holes 54, are defined through the ceiling forforming the recess 82. A plurality of punch holders 86, which are formedto have a rectangular parallelepiped-shaped configuration, are fitted tothe recess 82. The punch holders 86 are secured to the punchholder-fixing plate 62 by using screws 88 inserted into the holes 84.

[0052] As shown in FIG. 4, the punch holder 86 is defined with aplurality of long holes 90. A stamping punch 92 is inserted and securedinto each of the long holes 90. The stamping punch 92 includes a gripmember 94 and punch members 96 which are provided in an integratedmanner. The grip member 94 has a lengthy rectangular configurationincluding a plurality of long grooves 93 and circular arc-shapedcrosspieces 95 formed between the long grooves 93 which are formed onside walls in the longitudinal direction thereof. The punch member 96has a lengthy rectangular cross section including circular arc-shapedsections 97 which are formed at both ends in the longitudinal directionthereof. Each of the punch members 96 protrudes from the lower surfaceof the grip member 94 toward the die member 36.

[0053] In this arrangement, as in the first modified embodiment shown inFIG. 5, it is also preferable that forward ends of circular arc-shapedtops of the crosspieces 95, which are indicated by reference numeral 109and which are formed on the side walls of the grip member 94 a, aredeformed to include flat portions. Alternatively, as in the secondmodified embodiment shown in FIG. 6, it is also preferable that the sidewalls of the grip member 94 b are made flat, and the plurality of punchmembers 96 b have a pin-shaped configuration.

[0054] When the length of protrusion of the punch member 96 from thegrip member 94 is formed to be short, then the rigidity of the punchmember 96 is improved to decrease the fear of deformation and bucklingof the punch member 96. On the other hand, when the length is formed tobe long, then it is possible to increase the number of grindingoperations performed to use the worn punch member 96 again, and thus theservice life of the punch member 96 is prolonged.

[0055] As shown in FIGS. 1 and 3, a stripper-fixing plate 98 is arrangedunder the punch holder-fixing plate 62. The upper surface of thestripper-fixing plate 98 is fixed to the columnar members 66 by usingscrews 100. Subposts 102 a to 102 d, which penetrate through holes 103disposed in the vicinity of corners of the stripper-fixing plate 98 andwhich extend downwardly, are provided at lower portions of the punchholder-fixing plate 62. Therefore, the stripper-fixing plate 98 issupported such that it is capable of making approach and separation withrespect to the punch holder-fixing plate 62. As shown in FIG. 1, thelower portions of the subposts 102 a to 102 d are slidably inserted intothe holes 14 a to 14 d, 20 a to 20 d, 30 a to 30 d. Accordingly, whenthe upper die 48 makes the displacement in the direction to makeapproach or separation with respect to the lower die 18, the lower die18 and the upper die 48 are prevented from positional deviation by theaid of the main posts 26 a to 26 d and the subposts 102 a to 102 d.

[0056] A recess 104 is defined at a lower portion of the stripper-fixingplate 98. A plurality of strippers 106, which are formed to have arectangular parallelepiped-shaped configuration, are fitted to the walls105 for forming the recess 104. The stripper 106 is secured to thestripper-fixing plate 98 by using screws 108. A plurality of long holes110, through which the punch members 96 are slidably inserted, aredefined through the stripper 106. A recess 111 for advancing anunillustrated machining tool is defined on the upper surface of thestripper 106 in order to facilitate the perforating machining for thelong holes 110.

[0057] The stamping punching apparatus 10 according to the firstembodiment of the present invention is basically constructed asdescribed above. Next, its production process will be explained.

[0058] At first, explanation will be made with reference to FIGS. 7A to7D for the method for producing the grip member 94 and the punch members96.

[0059] As shown in FIG. 7A, a material such as a general cementedcarbide material is subjected to surface grinding machining for sixsurfaces by using an unillustrated surface grinding machine to form alengthy rectangular parallelepiped shaped configuration 99.Subsequently, as shown in FIG. 7B, long grooves 101 having a rectangularcross section are formed on two opposing side walls of the rectangularparallelepiped shaped configuration 99. Further, as shown in FIG. 7C,projections between the long grooves 101 on the side walls are formedinto crosspieces 95 having a circular arc-shaped cross section by usingan unillustrated numerical control machine tool.

[0060] Further, as shown in FIG. 7D, long grooves 107 having apredetermined depth are formed on another side wall so that the longgrooves 107 communicate with the long grooves 101 on the two side wallsdescribed above. Accordingly, the grip member 94 including the pluralityof long grooves 93 and the crosspieces 95 formed between the longgrooves 93 on the two side walls, and the plurality of punch members 96having a lengthy rectangular cross section with the circular arc-shapedsection 97 formed at the both ends are formed in an integrated manner.

[0061] Conventionally, the stamping punch has been formed by using anultra-fine grain cemented carbide material which is provided with a highhardness as well as a high toughness, and it is produced by performinggrinding by using a grinding stone or the like to form a punch member96. However, in the case of a soft workpiece such as a green sheet, thestamping load is small, and little wear occurs. Therefore, as describedin the embodiment of the present invention, the perforating machiningcan be applied by using the stamping punch 92 which is formed byprocessing the general cemented carbide material by means of theelectric discharge machining.

[0062] In this process, the grip member 94 and the punch members 96 areformed in the integrated manner. Therefore, the production steps for thestamping punch 92 can be simplified. Further, the rectangularparallelepiped shaped configuration 99, which has aflat surface with ahigh machining accuracy, is formed by using the surface grindingmachine. Furthermore, the circular arc-shaped crosspieces 95, which hasa high machining accuracy, are formed on the side walls of the gripmember 94 by using the NC machining machine. In this process, it is alsopreferable that the crosspiece 95 having the circular arc-shapedconfiguration with a flat top according to the first modified embodimentshown in FIG. 5 is formed by performing grinding by using the NCmachining machine while partially leaving the flat portion formed bysurface grinding machining, in place of the crosspiece 95 between thelong grooves 93 on the side wall formed to have the circular arc-shapedcross section by using the NC machining machine. The partially remainingflat portion has been previously formed by means of surface grindingmachining in which the accuracy can be easily obtained. Therefore, it ispossible to obtain the high flatness as compared with the formationperformed by using the NC machining machine.

[0063] During the production process, an intermediate inspection isperformed to confirm the fitting accuracy by inserting the stampingpunch 92 into the long hole 90 of the punch holder 86 (see FIG. 4) atthe stage at which surface grinding machining is applied to the sixsurfaces of the material (see FIG. 7A) and at the stage at which thelong grooves 101 are formed on the side walls of the rectangularparallelepiped shaped material 99 (see FIG. 7B) respectively. If anydefect in fitting accuracy is confirmed in the intermediate inspection,the machining is performed again for the purpose of repair. Therefore, adefective shaped is prevented without any subsequent production stepsbeing carried out in vain.

[0064] On the other hand, when the punch members 96 b having thepin-shaped configuration according to the second embodiment shown inFIG. 6 are formed, the punch members 96 b having the narrow spacingdistance or having the small diameter can be highly accurately producedby applying, for example, the wire electric discharge machining.

[0065] The stamping punch 92 thus produced is inserted and fitted intothe long hole 90 of the punch holder 86, and the portion of the gripmember 94 is secured by using an adhesive or the like.

[0066] In this process, if the grip member 94, which is joined to theside walls of the long hole 90 of the punch holder 86, has a flatsurface over its side walls, it is necessary to increase the machiningaccuracy in order to increase the fitting accuracy. On this condition,even if the fitting accuracy is increased, the adhesive merely entersthe minute gap between the joined surfaces. As a result, the adhesivestrength is defective, and it is impossible to obtain any good fittedstate. For example, problems arise in that the adhered portion is peeledoff during the punching process described later on, and the stampingpunch 92 is disengaged. In such a circumstance, it may be conceived thatforcible insertion or shrinkage fitting is performed upon the fitting.However, such a procedure is not preferred because the stress generatedthereby remains and strain is caused.

[0067] On the contrary, as in the first embodiment of the presentinvention shown in FIG. 8 and the first modified embodiment shown inFIG. 9, a sufficient gap 113 is provided for the joined surfaces whenthe fitting is performed. Accordingly, a large amount of adhesive can becontained in the space of the gap 113. Further, the expanding effect ofthe adhesive after the joining is also added, because the areal size ofthe joined surfaces is large on the side of the grip member 94. Thus, itis possible to obtain a large adhesive force.

[0068] In this state, the linear portion indicated by reference numeral115 in FIG. 8, or the flat portion indicated by reference numeral 109 inFIG. 9, which is formed and machined highly accurately by means of thesurface grinding machining for the six surfaces, remains at the top ofthe crosspiece 95 of the side wall of the grip member 95. These portionsslidably make line-to-line or surface-to-surface contact with the sidewalls of the long hole of the punch holder 86. Therefore, the fittingaccuracy is excellent.

[0069] Subsequently, as shown in FIG. 3, the punch holders 86 areinstalled to the recess 82 of the punch holder-fixing plate 62, and theyare secured by using the screws 88. As shown in FIG. 1, the punchmembers 96 are inserted into the holes 110 of the stripper 106, and thestripper 106 is secured to the stripper-fixing plate 98 by using thescrews 108.

[0070] Next, explanation will be made for the operation of the stampingpunching apparatus constructed as described above, especially for theoperation effected when the stamping punching apparatus 92 according tothe second modified embodiment (see FIG. 6) is used. At first, as shownin FIG. 1, a sheet material 120 such as a ceramic green sheet is placedon the die members 36.

[0071] Subsequently, when the upper die attachment member 42 is moveddownwardly in accordance with the action of an unillustrated drivingsource, the lower surface of the stripper 106 abuts against the uppersurface of the sheet material 120 as shown in FIG. 10. The sheetmaterial 120 is pressed against the stripper 106 by the aid of theresilient force of the spring member 72 shown in FIG. 1. Accordingly,the sheet material 120 is positioned, and it is prevented frompositional deviation.

[0072] When the upper die attachment member 42 is further moveddownwardly, the spring member 72 is contracted. As shown in FIG. 11, theforward ends of the punch members 96 protrude from the holes 110 of thestripper 106. Thus, long holes 122 are defined through the sheetmaterial 120.

[0073] In the present invention, the punch members 96 are formedintegrally with the grip members 94, and the grip members 94 are fittedto the punch holders 86 at a high degree of accuracy. Therefore, thepositional accuracy of the punch member is improved. Accordingly, thepositional accuracy and the shape accuracy of the long holes 122 definedthrough the sheet material 120 are improved. Further, the space betweenthe hole 122 and the adjoining hole 122 of the sheet material 120 isappropriately supported by the die member 36. Accordingly, the sheetmaterial 120 is prevented from inclination and breakage. Further, therigidity of the punch member is also improved, and hence no unbalancedload is exerted on the stripper.

[0074] Subsequently, when the unillustrated driving source is energizedin an opposite direction, then the upper die attachment member 42 ismoved upwardly, and the punch members 96 and the stripper 106 areseparated from the sheet material 120. Thus, the sheet material 120subjected to the perforating machining is obtained.

[0075] When the punch member 96 is broken or worn, and it is required tobe exchanged, then the stamping punch 92 including the punch member 96required to be exchanged is detached from the long hole 90 of the punchholder 86. Subsequently, a grip member 94 of a stamping punch 94 forexchange is inserted and secured into the long hole 90. The punch member96 is inserted into the hole 110 of the stripper 106. The punch members96 are easily inserted into the holes 110, because the respective punchmembers 96 have the high positional accuracy.

[0076] Next, a stamping punching apparatus according to the secondembodiment of the present invention will be explained in relation to theproduction process thereof. Explanation will be made below forcomponents or parts different from those of the stamping punchingapparatus 10 according to the first embodiment. The same components orparts as those of the first embodiment are designated by the samereference numerals in the drawings, detailed explanation of which willbe omitted.

[0077] As shown in FIG. 12, in this embodiment, the stamping punch 92 cis formed by the grip member 94 c divided into a plurality of componentsso that the punch members 96 c are interposed thereby. That is, the gripmember 94 c is constructed separately from the punch members 96 c inthis embodiment. The grip member 94 c used in this embodiment comprisesa first holding member 114 which is disposed at the center of the gripmember 94 c and which is formed to have a lengthy configuration. Bothside portions of the first holding member 114, which are disposed alongthe longitudinal direction, are formed as flat sections 115 a, 115 b.

[0078] A pair of second holding members 116 a, 116 b, which are formedto have a lengthy configuration, are arranged for the respective flatsections 115 a, 115 b. A plurality of grooves 124 are defined inparallel to one another in a direction perpendicular to the longitudinaldirection of the second holding member 116 a, 116 b, on the lengthy wallsurface of the second holding member 116 a, 116 b. The groove 124 isformed to have a substantially V-shaped configuration.

[0079] A recess 117 is defined on the bottom of the first holding member114. On the other hand, recesses 118 a, 118 b are defined on the secondholding members 116 a, 116 b. A chamber 123 is formed by the recess 117and the recesses 118 a, 118 b.

[0080] When a plurality of punch members 96 c are secured to the gripmember 94 c formed as described above, a fixing jig 130 is used. Thefixing jig 130 comprises a first jig 132 which is placed on an upperportion of the first holding member 114 and which is formed to have arectangular parallelepiped-shaped configuration, and second jigs 134 a,134 b which are placed on upper portions of the second holding members116 a, 116 b and which are defined with grooves 136 each having aV-shaped cross section communicating with the grooves 124. Bar members135 a, 135 b for gripping the first jig 132 are secured to upperportions of the first jig 132.

[0081] When the plurality of punch members 96 c are secured to the gripmember 94 c, the first jig 132 is firstly placed on the upper portion ofthe first holding member 114. In this state, the first holding member114 is separated from the second holding members 116 a, 116 b.Subsequently, when the second jigs 134 a, 134 b are placed on the secondholding members 116 a, 116 b, the grooves 124 communicate with thegrooves 136. Subsequently, the punch members 96 c are arranged in thegrooves 124 and the grooves 136.

[0082] The first holding member 114 is interposed by the second holdingmembers 116 a, 116 b, and the first jig 132 is interposed by the secondjigs 134 a, 134 b. Accordingly, as shown in FIG. 13, the plurality ofpunch members 96 c are positioned in parallel to one another by beinginterposed by the walls for forming the grooves 124, 136 and the wallsof the first holding member 114 and the second jigs 134 a, 134 b.

[0083] In this state, the punch members 96 c are interposed by the wallsfor forming the grooves 124, 136 and the walls of the first holdingmember 114 and the second jigs 134 a, 134 b, and they are positionedwith a high positional accuracy. As shown in FIG. 12, an adhesive ischarged into the chamber 123. When the adhesive is cured, the punchmembers 96 c are secured highly accurately by the first holding member114 and the second holding members 116 a, 116 b. Thus, the stampingpunch 92 is produced.

[0084] When the stamping punch 92 c is produced as described above, thepunch members 96 c can be highly accurately secured to the punch holder86, for example, even in the case of a minute punch in which the punchmember 96 c has a diameter of not more than 0.3 mm. The plurality ofpunch members 96 c are aligned on one grip member 94 c. Therefore, it ispossible to arbitrarily select the number of stamping punches 92 cnecessary for one stamping punching apparatus.

[0085] Subsequently, as shown in FIG. 4, the stamping punch 92 isinserted into the long hole 90 of the punch holder 86 in the same manneras in the first embodiment (the other constitutive components except forthe stamping punch 92 and the punch holder 86 of the second embodimentare the same as those of the first embodiment, and explanation will bemade below by using the drawings and reference numerals described in thefirst embodiment).

[0086] As shown in FIG. 3, the punch holders 86 are installed to therecess 82 of the punch holder-fixing plate 62, and they are secured byusing the screws 88. Subsequently, as shown in FIG. 1, the punch members96 are inserted into the holes 110 of the stripper 106. The stripper 106is secured to the stripper-fixing plate 98 by using the screws 108.Thus, the stamping punching apparatus is obtained.

[0087] In the stamping punching apparatus according to the secondembodiment described above, the punch member 96 is formed to have thecircular cross section. However, other configurations are available,including, for example, oblong or elliptic configurations. Further, thegrip member 94 may be formed to connect the plurality of punch members96.

What is claimed is:
 1. A method for producing a punching apparatus forstamping comprising a punch holder secured to an upper die, a die membersecured to a lower die, a plurality of grip members detachably fastenedto said punch holder, and said plurality of punch members formed on eachof said plurality of grip members, said method comprising said steps of:using a prism-shaped block as a material for said grip member and saidpunch members; machining a plurality of parallel long grooves separatedfrom each other by arbitrary spacing distances on two opposing sidewalls of said prism-shaped block; machining tops of crosspieces formedbetween said long grooves to have a circular arc-shaped configuration;machining long grooves having an arbitrary depth on another side wall sothat said long grooves communicate with said long grooves on said twoside walls; simultaneously forming thereby said grip member includingsaid plurality of long grooves and said circular arc-shaped crosspiecesformed between said long grooves provided on said two opposing sidewalls and said plurality of punch members each having a lengthyrectangular cross section with its both ends provided with circulararc-shaped portions; and defining a plurality of holes each having arectangular cross section on said punch holder on the other hand,wherein: said grip member is fitted to said punch holder with a gap suchthat said crosspieces formed on said side walls of said grip memberslidably contact with side walls of said hole of said punch holder. 2.The method for producing said punching apparatus for stamping accordingto claim 1, wherein said circular arc-shaped top of said crosspieceformed on said side wall of said grip member and said circulararc-shaped portion of said punch member are deformed to include flatportions.